This proposal discusses the development of mammaglobin as a marker for the diagnosis of breast cancer and the monitoring of residual breast cancer disease. Breast cancer results in the death of 40,000-50,000 women in the U.S. annually. Early detection of this disease is critical for effective treatment and currently available procedures lack the necessary sensitivity and specificity. Work at Corixa has demonstrated that both the mammaglobin gene and the secreted mammaglobin protein can be detected in the blood of women with breast cancer. We have initiated development of two assays based on the high degree of expression specificity of the mammaglobin gene. One assay is based on quantitative PCR of captured epithelial cells from peripheral blood to detect anchorage-independent breast tumor cells. The second assay is a sandwich ELISA to detect mammaglobin protein in the blood of women with breast cancer using existing antibodies developed at Corixa. The development of these assays, in combination with collaborations with key investigators in the area of breast cancer, and access to an extensive blood and tissue bank, should enable the goals and objectives of this proposal to be achieved. PROPOSED COMMERCIAL APPLICATIONS: The proposed studies will lead to commercialization of a real time PCR assay and/or antigen detection assay for the diagnosis of breast cancer and the monitoring of residual breast cancer disease. Such tests would be marketed in the U.S. and worldwide. The estimated market for such a test is $200-300 million per year.